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    Subject[PATCH v2 0/5] ipc: Clamp *mni to the real IPCMNI limit
    Date
    v1->v2:
    - Add kdoc comments to the do_proc_do{u}intvec_minmax_conv_param
    structures.
    - Add a new flags field to the ctl_table structure for specifying
    whether range clamping should be activated instead of adding new
    sysctl parameter handlers.
    - Clamp the semmni value embedded in the multi-values sem parameter.

    v1 patch: https://lkml.org/lkml/2018/2/19/453

    The sysctl parameters msgmni, shmmni and semmni have an inherent limit
    of IPC_MNI (32k). However, users may not be aware of that because they
    can write a value much higher than that without getting any error or
    notification. Reading the parameters back will show the newly written
    values which are not real.

    Enforcing the limit by failing sysctl parameter write, however, can
    break existing user applications. To address this delemma, a new flags
    field is introduced into the ctl_table. The value CTL_FLAGS_CLAMP_RANGE
    can be added to any ctl_table entries to enable a looser range clamping
    without returning any error. For example,

    .flags = CTL_FLAGS_CLAMP_RANGE,

    This flags value are now used for the range checking of shmmni,
    msgmni and semmni without breaking existing applications. If any out
    of range value is written to those sysctl parameters, the following
    warning will be printed instead.

    Kernel parameter "shmmni" was set out of range [0, 32768], clamped to 32768.

    Reading the values back will show 32768 instead of some fake values.

    Waiman Long (5):
    sysctl: Add kdoc comments to do_proc_do{u}intvec_minmax_conv_param
    sysctl: Add flags to support min/max range clamping
    sysctl: Warn when a clamped sysctl parameter is set out of range
    ipc: Clamp msgmni and shmmni to the real IPCMNI limit
    ipc: Clamp semmni to the real IPCMNI limit

    include/linux/sysctl.h | 7 ++++
    ipc/ipc_sysctl.c | 29 +++++++++++--
    ipc/sem.c | 33 +++++++++++++++
    ipc/util.h | 4 ++
    kernel/sysctl.c | 111 +++++++++++++++++++++++++++++++++++++++++++++----
    5 files changed, 173 insertions(+), 11 deletions(-)

    --
    1.8.3.1

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